The present disclosure relates to an image forming apparatus that supplies power to a device connected to a connector.
A PC may be connected to a peripheral device. When a main power supply is turned on, the PC main body starts to operate. During a start-up process, it is checked whether or not a peripheral device is connected. In order to check whether or not a peripheral device is connected, it is necessary that the peripheral device is supplied with power and has started up. When a start-up time of the peripheral device is long, it may take time to start up the BIOS and OS of the PC main body. For this reason, an example of technique for shortening start-up time of the BIOS and OS is known as below.
Specifically, there is known a peripheral device having a delay mode in which it starts up after the OS of the PC has started up. In the delay mode, after being supplied with power from the PC, the device waits until a delay time stored in it elapses. After the delay time elapses, the device performs plug-and-play connection to the PC. In this way, the PC does not detect the peripheral device during start-up of the BIOS and OS. Thus, start-up time of the BIOS and OS is shortened.
An image forming apparatus such as a multifunction peripheral, a copier, a printer, or a FAX device may be provided with a connector. This connector is used for connecting a storage device such as a USB memory or a memory card, or an input device such as a keyboard. For example, using data stored in a connected storage device, the image forming apparatus can perform printing and transmission.
A control circuit such as a CPU in the image forming apparatus (host, main body side) transmits a call (request) to the device via the connector. The device connected to the connector responds to the request and replies a response. In this way, communication is performed between the control circuit and the device. On the basis of the communication with the device, the control circuit recognizes presence or absence of connection of the device, and recognizes which device is connected.
Here, the time after the control circuit issues the request until the device is finally recognized (response time of the device) is different depending on the device. For example, the USB standard does not define the time after the control circuit issues the request until the device is recognized. The time has a variation depending on the device. As slower the device responds, the time until the control circuit recognizes the device becomes longer. In the USB standard that supports increasing types of devices, the time limit after the request until the control circuit recognizes the device is being relieved.
From a viewpoint of security, the image forming apparatus may impose a restriction of use of specific data that adds a change to the backbone of the system. The specific data can be used only when the device is recognized and the specific data can be read within a predetermined time after the start-up process is started after the main power supply is turned on. Specifically, the device storing the specific data is connected before the main power supply is turned on. Then, the process based on the specific data is started only when the control circuit recognizes the device and the specific data can be read within the predetermined time after the start-up process is started after the main power supply is turned on.
However, when using a device having a slow response, the control circuit may not be able to recognize the device within a predetermined time after the start-up process is started. The control circuit may recognize connection of the device after the start-up process is completed. Otherwise, the control circuit may recognize connection of the device after the start-up process has proceeded to a stage such that the process based on the specific data cannot be started. In this way, there is a problem that a device having a slow response cannot be used. It is necessary to check a device having a time until being recognized within a permissible range (device having a short response time) among many available devices in the market, and this is inconvenient.
It is considered to set a standby time for interrupting the start-up process to recognize the device, so that the process based on the specific data can be performed regardless of length of the response time. However, when the start-up process is interrupted, the time necessary for the start-up process is increased. In addition, wasteful waiting occurs in a case where no device is connected.
The above-mentioned known technique decreases start-up time of the BIOS and OS. This technique does not check connection of the device during the start-up process. During the start-up process, data cannot be read from the device. In addition, there is no description about length of time until the connection is recognized. Therefore the problem described above cannot be solved.